Long-term objectives: To develop behavioral techniques for the assessment of vision in human infants, and to carry out substantive studies of the development of specific visual functions. Specific Aims: 1. To develop techniques for controlling the retinal locations of stimuli, in order to test near-foveal (central) and peripheral visual function separately. 2. To conduct substantive studies of (a) absolute thresholds and spectral sensitivity in central vision, and (b) characteristics of spatial summation and resolution (Ricco areas and Westheimer functions) in peripheral vision. 3. To continue exploration of the statistical properties of two-alternative forced-choice (2 AFC) psychophysical techniques, especially as these properties apply to infant vision testing. 4. To continue the development of "Acuity cards", a rapid acuity assessment technique intended for eventual use in clinical settings.